1. Field of the Invention
The present invention relates to an apparatus for X-ray photography of the area of the dentition and of the jaws, and of the type comprising a stationary frame part, a bearing part which is movably mounted to the frame part and preferably performs a linear movement, and a support arm which is rotatably attached using bearings to the bearing part and has at one end a source of X-radiation and at the opposite end a movable X-ray film, the movements of the bearing part, the support arm and the film being synchronized in such a way that a sharp image of only an area of the desired shape is obtained on the film, for example the area of the patient's dental arch.
2. Description of the Prior Art
In panoramic X-ray photography it is known, in order to obtain a sharp image of the dental arch, to allow the rotational axis of the support arm to move during the exposure in a predetermined manner linearly or non-linearly in such a way that this movement is dependent on the angular position of the support arm at each given time. The movement of the rotational axis may be linear, and parallel to the axis of symmetry of the dental arch, perpendicular to it, curved, or noncontinous between predetermined points. The enlargement can be adjusted by shifting the location of the patient, i.e. the head-supporting devices, in relation to the support arm. It is also known to change the patient's position so that the X-ray tube travels in relation to the patient either around the face or around the neck.
In practice the shifting and repositioning of the patient is always cumbersome and time-consuming. Furthermore, the known X-ray photography apparatus do not always provide so extensive possibilities for positioning and use as are generally desired in order to obtain a precise image of some specific area or part of an area.